1. Field of the Invention
The present invention relates to a speed limiter that recognizes a speed limit for a road on which a subject vehicle is traveling, based on an image captured by a front monitoring camera, and changes characteristics of throttle opening with respect to accelerator opening when a difference between the speed of the vehicle and the speed limit exceeds a predetermined value.
2. Description of the Related Art
A driver generally recognizes a speed limit displayed on a road sign or a road-surface sign on a road to determine whether or not the speed of a subject vehicle is within the speed limit. When the vehicle speed exceeds the speed limit, the driver controls the vehicle speed by performing a decelerating operation such as a reduction in a pressing amount of the accelerator pedal so as to make the vehicle speed fall within the speed limit.
However, it is difficult to operate the vehicle while constantly recognizing the vehicle speed of the traveling road. It frequently occurs that the driver drives at a normal legal speed, missing a road sign or misunderstanding that a speed limit is not set for the traveling road.
As means for preventing an overspeed due to the carelessness of the driver described above, there is known a technology that detects the position of a subject vehicle using a car navigation system, reads speed limit data stored in map data, and gives an alarm when the speed of the subject vehicle exceeds the speed limit.
However, the speed limit is periodically changed, and sometimes a new road is open. Although it is possible to accommodate these cases by updated the map data, the update of the map data at short intervals requires a significant cost, and thus is not realistic.
An alternative technology is to recognize the speed limit based on information from a beacon using a light or radio wave that is installed on a side of a road. However, when the vehicle is traveling in a region where a beacon cannot be received, accurate speed limit information cannot be obtained.
In light of this, for example, Japanese Unexamined Patent Application Publication No. 2007-199026 discloses a technology that recognizes a speed limit displayed on a speed sign based on an image captured by a front monitoring camera, displays both an actual vehicle speed and the speed limit on an instrument panel, and, when the actual vehicle speed exceeds the speed limit, gives a warning by coloring a speed excess region.
According to the technology disclosed in Japanese Unexamined Patent Application Publication No. 2007-199026, since the speed limit is recognized based on the image captured by the front monitoring camera, the driver can be always informed of the latest seed limit.
There is also known a device that, when an overspeed is detected, makes a warning as well as activates a speed limiter to encourage the driver to drive within a speed limit.
The device may activate the limiter and limit the speed without exception whenever the actual vehicle speed exceeds the speed limit. In this case, if, for example, vehicles are traveling with a short inter-vehicle distance on a crowded road and only the speed of the subject vehicle is limited, following vehicles are prevented from running smoothly, and moreover, the subject vehicle may cause congestion.